Catheter introducer

Abstract

A catheter introducer assembly includes an introducer sheath mounted on a dilator. The distal end of the dilator protrudes beyond the distal end of the sheath and defines an arrowhead having a proximally facing surface that cooperates with the distal end of the sheath to reduce the risk of tissue trauma while facilitating smooth entry into and through tissue. The proximal hubs of the dilator and sheath are configured with respect to the relation between the distal end of the dilator and sheath to provide smooth controlled withdrawal of the dilator through the sheath. The sheath is attached, at its proximal end, to a housing with a mechanical connection that does not require the use of adhesives, welding or other bonding techniques. The connection also may incorporate an integral strain relief for the proximal end of the sheath. The housing at the proximal end of the sheath includes a proximal end cap construction that is secure and is easily attached without requiring ultrasonic welding or other bonding techniques. Methods are described for assembling the introducer and for forming the arrowhead portion of the dilator.

Having thus described the invention, what we desire to claim and secure by Letters Patent is: 
     
       1. A catheter introducer assembly comprising: an elongate tubular single layer sheath including proximal and distal ends, said sheath having a housing with an aperture at its proximal end;   a dilator having an elongate shaft including proximal and distal ends said dilator having a hub at its proximal end, the shaft extending though the aperture, the housing and the tubular sheath;   the distal end of the dilator having a radially enlarged dilation member having a proximally extending taper and a substantially uniform distally extending taper;   the housing and the hub being detachably connected to each other; and   the sheath having a length such that when the housing and the hub are fully connected, the distal end of the sheath is disposed proximally of the proximally extending taper of the dilation member and is in contact with the dilator shaft.   
     
     
       2. A catheter introducer assembly comprising: an elongate tubular sheath including proximal and distal ends, said sheath having a housing with an aperture at its proximal end;   a dilator having an elongate shaft including proximal and distal ends, said dilator having a hub at its proximal end, the shaft extending though the aperture, the housing and the tubular sheath;   the distal end of the dilator having a radially enlarged dilation member having a proximally facing surface and a distally facing surface;   the housing and the hub being detachably connected to each other; and   the sheath having a length such that when the housing and the hub are fully connected, the distal end of the sheath is disposed proximally of the proximally facing surface of the dilation member and is in contact with the dilator shaft;   wherein the housing and the hub are threadably connected to cause simultaneous rotary and axial motion of the dilator relative to the sheath during detachment and withdrawal of the dilator at least during an initial portion of said detachment and dilator withdrawal.   
     
     
       3. A catheter introducer assembly as defined in claim 2, further comprising a space between the distal end of the sheath and the proximally facing surface of the dilation member and wherein said axial motion of said initial portion of said detachment and dilator withdrawal is greater than an axial length of said space. 
     
     
       4. A catheter introducer assembly as defined in claim 3, wherein said axial motion is at least as long as a distance from the distal end of the sheath to a region of maximum diameter of the dilation member. 
     
     
       5. A catheter introducer assembly as defined in claim 1, wherein the distal end of the sheath terminates at an end wall having a radial extension not substantially more than a radial extension defined at a maximum diameter of the dilation member. 
     
     
       6. A catheter introducer assembly as defined in claim 1 wherein the distal end of the sheath terminates in an end wall having a radial extension of not more than about 0.002 inch beyond a radial extension of the dilation member at a region of its maximum diameter. 
     
     
       7. A catheter introducer assembly as defined in claim 1, wherein the tubular sheath is formed from a material that is softer than a material from which the dilator is formed, and the dilation member is larger in diameter than an inner diameter of at least a portion of the sheath. 
     
     
       8. A catheter introducer assembly as defined in claim 2 wherein: the distally facing surface of the radially enlarged dilation member comprises an elongate distal taper;   the proximally facing surface of the radially enlarged dilation member comprises a proximal taper substantially shorter than the distal taper; and   a region of transition from the proximal taper to the distal taper defines a maximum diameter of the radially enlarged dilation member.   
     
     
       9. A catheter introducer assembly as defined in claim 8 wherein the proximal taper defines a cone angle of about 90°. 
     
     
       10. A catheter introducer assembly as defined in claim 9 wherein the radial extension of the maximum diameter of the radially enlarged dilation member beyond the diameter of the dilator shaft is not substantially more that about two to three thousandths of an inch. 
     
     
       11. A catheter introducer assembly as defined in either one of claims 8 or 9 wherein a space between the distal end of the sheath and the proximally facing surface of the dilation member is in the range of about 0.002 to about 0.030 inch and the radial extension of the distal end of the sheath is up to about 0.002 inch beyond the radial extension at the maximum diameter of the dilation member. 
     
     
       12. A catheter introducer assembly as defined in either one of claims 8 or 9 wherein a space between the distal end of the sheath and the proximally facing surface of the dilation member is in the range of about 0.002 to about 0.020 inch and the radial extension of the distal end of the sheath is up to about 0.002 inch beyond the radial extension at the maximum diameter of the dilation member. 
     
     
       13. A catheter introducer assembly as defined in either one of claims 8 or 9 wherein a space between the distal end of the sheath and the proximally facing surface of the dilation member is about 0.010 inch and the radial extension of the distal end of the sheath is up to about 0.002 inch beyond the radial extension at the maximum diameter of the dilation member. 
     
     
       14. A catheter introducer comprising: an elongate tubular sheath having proximal and distal ends;   a housing attached to the proximal end of the sheath, the housing having a body and a distally extending nipple extending from the body, the proximal end of the sheath being disposed on the nipple and a distal cap snap-fit to the body to capture snugly the sheath between the nipple and the distal cap,   wherein the nipple has an irregular outer contour and the cap has an inner bore receptive to the irregular contour in a close fit.   
     
     
       15. The catheter introducer as defined in claim 14 wherein the irregular contour comprises the nipple being substantially tubular and having an annular barb disposed about its outer surface. 
     
     
       16. A catheter introducer as defined in any one of claims 14 or 15 wherein the distal cap is formed from an elastic material that is softer and more flexible than that of the body, the cap being adapted to elastically yield when assembled about the region of the nipple to constrict the proximal end of the sheath onto and about the nipple. 
     
     
       17. A catheter introducer as defined in claim 14 wherein the cap is formed to include an integral distal extension defining a strain relief about the sheath. 
     
     
       18. A catheter introducer as defined in claim 17 wherein the cap and strain relief extension are integrally molded from a flexible elastomeric material. 
     
     
       19. A catheter introducer as defined in claim 18 wherein the strain relief extension is of reduced cross-sectional dimension in a distal direction.